Hydraulic pump and motor



G. H. HUTCHISON ET AL HYDRAULIC PUMP AND MOTOR 'Filed May 2 1922 s Sheets-Sheet 1 FIG! ln en -zsx HYDRAULIC PUMP AND MOTOR Filed May 25, 1922 FIGZ :5 Shets-Sheet 2 WMU W Dec. 9, 1924- 1,518,851

G. H. HUTCHISON ET AL 7 HYDRAULIC PUMP AND MOTOR Filed May 25, 1922 3 Sheets-Sheet 5 lllllllmr HIP I wen f r-.5,-

W. JLJM Patented Dec; 9, 1924.

UNITED STATES PATENT OFFICE.

GEORGE HERBERT HUTGHISON, OFCHYNDLAND, GLASGOW, AND DAVID MOLEAN, F MARYHILL, GLASGOW, SCOTLAND.

HYDRAULIC PUMP A ND MOTOR.

Application filed May 25, 1922. Serial No. 563,621.

To all whom it may concern:

Be it known that we, GEORGE HERBERT HUTCHISON, of 36 Clarence Drive, Hyndland, Glasgow, and DAVID SMITH MoLEAN,

of 52 Guthrie Street, Maryhill, Glasgow, Scotland, both subjects of the King of Great Britain, have invented certain new and useful Improvements in Hydraulic Pumps and Motors, of which the following is a specification.

This invention relates to hydraulic pumps and motors of the type in which a series of pistons are housed in cylinders or recesses arranged radially in a rotor member, and

cooperate with an annular eccentric ring or track of which the eccentricity may be varied by a displacement of the ring bodily in a direction at right angles to the axis of the rotor. Single machines of this type may be employed either as pumps or motors while two exactly similar rotors may be mounted within a single casing to form a variable speed transmission gear, one rotor being driven as a pump to supply fluid under pressure to the other rotor which acts as a motor.

In pumps and motors of this type it is common practice to employ plunger or trunk pistons normally forced outwards by centrifugal force in conjunction with a cylindrical roller which is carried by the piston and takes the radial thrust between the piston and the track ring. In all such constructions, however, while the roller takes the radial thrust on the piston, no satisfactory provision has been made for taking the tangential thrust due to the relative rotation between the rotor and the track ring, and as this thrust is generally taken by the sliding contact of the piston body with the cylinder walls, very rapid wear of the pistons and cylinders takes place with the result that leakage of the working fluid past the piston soon develops, and the pump or motor has a very short life. This excessive wear is particularly marked when the roller axis is some distance from the cent-re of the piston, the turning moment about the centre of the piston producing a rocking action between the cylinder and piston which rapidly causes the piston to be worn oval.

It is also common practice to employ a central tubular valve about which the rotor member revolves, and within the body of which are formed passages on either side of an axial diaphragm or partition, the passages serving as discharge and inlet passages respectively and communicating with the radial cylinder through suitable ports in the Walls of the tubular valve, but with this type of valve the cross sectional area of the passages is necessarily limited and. there is a considerable loss of efiiciency due to friction between the working fluid and the walls of the passages, and also owing to the abrupt change in the direction of the fluid between the radial ports and the supply and discharge passages which are parallel to the axis.

The object of this invention is to provide an improved construction in which the tangential thrust between the cylinder and piston and the radial thrust between the piston and track ring are each taken by a roller or rollers located within the body of the piston so that the wear of the piston is eliminated,

and the life of a pump or motor is indefinitely prolonged, and in which the cross sectional area of the valve passages for the fluid is a maximum and all changes in the direction of the fluid are brought about gradually and naturally so that losses due to shock and eddying of the fluid are reduced to a minimum.

Our invention is illustrated in the accompanying drawings as applied to an hydraulic pump or to an hydraulic motor where two similar machines are mounted in a single casing, in the known manner, to form an infinitely variable transmission gear.

In the drawings Figure 1 is a part sectional view of a complete pump or motor with the cover plate removed showing the general arrangement.

Figure 2 is a sectional side elevation of the pump. or motor showing the valve member in section.

Figure 3 is a sectional plan on the line 83 of Fig. 2 the valve-member and cover plate being shown in full.

Fig. 4 is a sectional elevation of one of the pistons shown in Figs. 1 to 3; Fig. 5 is a section through one cylinder of the rotor.

Similar letters refer to similar parts throughout the drawings.

Referring to the drawings 1 is the rotor which may be either a casting or forging of any suitable metal, and is rotatably housed in the casing 2. The casing 2 is preferably a hollow cylindrical casting of the form shown, having means by which it may be bolted down to a suitable bedplate,-and having at one end a cover plate 2' which is bolted to the casing. 1

.In the body iof the rotor .are formed a number of radial cylindrical apertures or recesses 3, each communicating by a port 4 with a single central axial passage or chamber 5-. Seven'of thesecylindricalrecesses are shown in the drawings, but the number may be varied for. pumps of different sizes.

Each recess .3 forms a a iston 6 is free to slide.

ach piston comprises a slotted body cylinder in which member having a short cylindrical portion 7 of such a diameter as to be a smooth work- 'ing fit in its cylinder 3.

Housed in an axial slot in the piston are rollers 8 and 8'.

internal diameter of the cylinder so thatfit is a rolling fit therein, .the contour of the periphery of the roller being substantially of the rollers is a forced-fit in the piston body, and the rollers 8, 8, are rotatably carried thereon by a series of small roller bearings arranged between the roller bodies and the central portion of the spindle, so that each roller is free to rotate independently in the piston, the axes of the rollers being parallel to the axis of the annular track ring 11, against the inner surface of which the cylindrical rollers 8' abut. This track ring 11 is a T-section, with a slot in thehead to allow the free rotation of the spherical roller 8, the head being inwardly directed and the stem being held'by a retaining ring 12 in an outer ring .13 to which the retaining ring 12 is secured by screws 14. There is thus formed on either side of the track-ring an annular groove or recess 15 into which project pins 16 carried by the tapered upper portion of the piston body.

The pins 16 are preferably formed as short cylindrical members which are a driving fit in the side portions of the piston and pinnedtherein, the lower half'of the projecting portionsbeing cut away to fit freely into the grooves 15. These pins 16 serve to retain the piston rollers 8 in contact with the track-ring 11 and make the piston positive-acting on the suction stroke, particularly when the ump is running light. They also precludg any possibility of the piston twisting round should the-centrifugal force of the rotating piston be insuflicient' to keep the piston pressed outwards against the track-ring. The outer ring 13 which carries the trackring is mounted between a pair of slides or k The central roller 8 is of a diameter approximately equal to the gland; 1 9 through the medium of t e T- headed screw member 20 to vary the eccen- 'tricity of the track ring with regard to the rotor-in'the' manner known in pumps of-this type.

As the rotor body 'is rotated the cooperation of the two piston rollers 8' with the eccentrically mounted track-ring causes each piston to move inwards and outwards in its cylinder on alternate suction and compression strokes. Durin each working stroke the three forcesactmg on the piston are, the reaction of the track on der rollers 8, the fluid. pressure on the base of the piston, and the resultant thrust between the part-spherical roller 8 and the cylinder walls. I

The line of action of each of these forces passes through the 'axis of the spindle 9, since we have pure rolling with the rollers 8 and 8,'and a direct force of the piston. There is thus. perfect balance of all the forces acting and the work.

'ing conditions are nearly as ideal as is possible'in practice. Since the external forces are wholly taken by the rollers 8 and 8, the fluid pressure is the only force acting on the piston body and since the line of action of the force, the axis of the piston, and the axis of the cylinder are all concentric, the piston is a perfect floating fit, and subjects the cylinder sides to practically no wear and tear. The piston and cylinder are, therefore, not subjected to harmful strains and stresses by any of the forces actcorrespondingly increased.-

Circumferential grooves or recesses 25 are ing and the'life of the mechanism is thus grooves passing through the upper ends of the cylinder recesses in the rotor, as shown substantially equal to the internal diameter of the axial chamber in the rotor, andisrigidly'secured to or formed integral with the cover plate 2 which is boltedto the casing 2.

Portions of the valve member are cut away on opposite sides of the axis as shown to leave a central partition. which divides the axial chamber in the rotor into two pas sages 27, 28, one of which forms the disthe cylinalong the axis formed in the periphery of the rotor 1 to receive the recessed track ring 11, the

charge, and the other the inlet passe e, their respective functions depending on t e position of the track-ring 11, in the manner known in hydraulic pumps and motors of this t pe.

Eac cylinder 3 communicates with the axial chamber in the rotor through the port 4 and the portions of the valve member 26 at the. end of each passage 27, 28, adjacent to the ports in the rotor are carefully rounded off as shown at 29, 29, so that the change in direction of the fluid both on the discharge and on the inlet side of the valve member may be as gradual as possible to avoid losses due to shock and eddy.

Itis obvious from the configuration of the valve that every part thereof may be readily machined in manufacture, and the axial chamber in the rotor is also machined so that all the surfaces with which the working fluid is in contact in its passage through the pump or motor are smooth, and losses due to fluid friction are reduced to a minimum, with the result that the hydraulic eflicieney 0f the machine as a whole is very high.

To prevent leakage of the working fluid from one side of the valve piece to the other, there is provided the bearing plate 30 which is forced against a1 recess in the face of the rotor by a number, say, eight, of small springs 31, located in a groove at the back of the plate 30, and abutting against the inner race of the roller bearing 32. Two keys or tongues project from the back of the bearing plate 30 at the top and bottom thereof and engage in the key-ways 33 on a boss 34 on the valve member. These keys serve to prevent the bearing plate from turning with the rotor and also to prevent leakage of the working fluid around the back of the bearing plate from the pressure to the suction side. The boss 34 also serves to carry the inner race of the roller bearing 32 of which the outer race is housed in a recess in the end of the rotor. This hearing 32 takes up anyside thrust which exists due to the presence of high pressure fluid on one side of the valve member and low pressure fluid on the other. An extension 35 on the inner end of the valve- .member carries a second roller bearing 36 for the rotor, and a ball thrust bearing 37 between the back of the rotor and the casing takes up any end thrust on the rotor.

An oil tight bush 38 is preferably provided in the casing where the shaft 39 of the rotor passes through it and any referred means may be provided on the shaft 39 for coupling to a prime mover or to a machine to be driven.

In Fig. 2 are shown passages 40 of small diameter leading from the inner face of the rotor to the back thereof. These are provided to prevent any working fluid which may leak past the valve from collecting between the rotor and the inner end of the valve, as they allow any such fluid to pass through the body of the rotor into the main part of the casing.

We claim: I

1. An hydraulic pump or motor comprising a casing, a rotor rotatably mounted within the casing, an annular eccentric track-ring slidably mounted within the casing around the rotor, pistons sliding within radial cylinders formed in the rotor and cooperating with the said track-ring, passages for the supply and discharge of the working fluid to and from said 'ylinders, a roller rotatably mounted within the body of each piston to take the tangential thrust between the piston and the cylinder walls, and a cylindrical rotatably mounted roller on each side of the said roller to take the radial thrust between the piston and the track ring.

2. An hydraulic pump or motor comprising a casing, a. rotor rotatably mounted within the casing, an annular eccentric track-rin ,slidably mounted within the casing around the rotor, pistons sliding within radial cylinders formed in the rotor and co-operating with the said track-ring, passages for the supp-1y and discharge of the working fluid to and from said cylinders, a roller rotatably mounted within the body of each piston to take the tangential thrust between the piston and the cylinder walls, and a cylindrical rotatably mounted roller on each side of the said roller to take the radial thrust between the piston and the track ring, the inner face of the track-ring being recessed centrally to clear the central roller, and the rotor being recessed to clear the parts of the gravel: ring upon which the cylindrical rollers ear.

3. An hydraulic pump or motor comprising a casing, a rotor rotatably mounted within the casing, an annular eccentric track-ring slidably mounted within the casing around the rotor, pistons sliding within radial cylinders formed in the rotor and co-o-perating with the said track-ring, passages for the supply and discharge of the working fluid to and from said cylinders, a roller rotatably mounted within the body of each piston to take the tangential thrust between the piston and the cylinder walls, and a cylindrical rotatably mounted roller on each side of the said roller to take the radial thrust between the piston and the track ring, the central roller being of a diameter substantially equal to the diameter of the piston and its periphery being in configuration the central zone of a sphere.

4. An hydraulic pump or motor comprising a casing, a rotor rotatably mounted within the casing, an annular eccentric trackring slidably ,mounted within the casing around the rotor, pistons sliding within radial cylinders formed in the rotor and cooperating with the .said track ring, passages for the supply and discharge of the working fluid to and from said cylinders, a roller rotatably mounted within the body of each piston to take the tangential thrust between the piston and the cylinder walls, a cylindrical. rotatably mounted roller on each side of the said roller to take the radial thrust between the piston and the track-ring, and means carried on dxtensions of the piston to engage within annular grooves in the side faces of the track ring and retain the said cylindrical rollers in engagement with the track-ring.

5. An hydraulic pump or motor comprising a casing, a rotor rotatably mounted within the casing, an annular eccentric track-ring slidably mounted within the easing around the rotor, pistons sliding within radial cylinders formed in the rotor and c0- operating with the said track-ring, a roller rotatably mounted within the body of each piston to take the tan ential thrust between the piston and the cy inder walls, a cyl ndrical rotatably mounted roller on eachside of the said roller to'take the radial thrustbetween thepiston and the track-ring,' a port at the inner end of each cylinder communicating with an axial cylindrical chamber in therotor', and means dividing the said chamber axially into sup] ly and discharge passages for the working fluid.

6. An hydraulic pump or motor comprising a casing, a rotor rotatably mounted within the casing, an annular eccentric track-ring slidably mounted within the easing around the rotor, pistons sliding within radial cylinders formed in the rotor and cooperating with the said track-ring, a roller rotatably mounted within the body of each piston to take the tan ential thrust between the piston and the cydinder walls, a cylinrounded off at the ends of the passages tocause the change in the direction of the fluid to take place gradually and without shock.

7. An hydraulic pump or motor comprising a casing, a rotor rotatably mounted within the casing, an annular eccentric truck-ring sli dably mounted within the 0518-.

ing around the rotor, pistons sliding within radial cylinders formed in the rotor and 00-" operating with the said track-ring, a roller rotatably mounted within the body of each piston to take the tangential thrust between the piston and the cylinder walls, a cylindrical rotatably mounted roller on each side of the said roller to take the radial thrust between the iston and the track ring, an axial cylin rical chamber being provided in the rotor with which the cylinders are in communication through radial ports at their innerends, a fixed cylindrical valve member dividing the said chamber into supply and discharge passages, "cylin drical extensions on the said valve member carrying roller bearings for the rotor, and an annular bearin plate keyed to the said valve memberanti resiliently held against the face of the rotor to prevent leakage of the working fluid between the rotor and the valve member.

In testimony whereof we afiix our signatures. A

GEORGE HERBERT HUTCHISON. DAVID SMITH Mel-BAN. 

